Positive temperature coefficient compensation for PT100 temperature sensor

Temperature is a very important physical parameter. Thermocouples and thermistors (RTDs) are suitable for most high temperature measurements, but designers must select the appropriate sensor for a specific application. Table 1 provides a selection guide for commonly used sensors.

Table 1. Sensor characteristics

RTD has high accuracy and operating temperature range: -200°C to +850°C. They also have good long-term stability and their temperature output can be transmitted, displayed and recorded using appropriate data processing equipment. Because the thermistor's resistance is proportional to temperature, designers can obtain an output voltage proportional to temperature simply by flowing a known current through the resistor. Based on the known resistance-temperature relationship, the measured temperature value can be calculated.

The change in resistance value with temperature is called the "temperature coefficient of resistance". The temperature coefficient of most metal materials is positive, and the temperature coefficient of many pure metal materials remains constant within a certain temperature range. Therefore, the thermistor is a stable, high-precision temperature detector with linear response. Which metal material (platinum, copper, nickel, etc.) is selected for a specific application depends on the temperature range being measured.

The nominal resistance value of a platinum resistor is 100Ω at 0°C. Although an RTD is a standardized device, there are many different standards used around the world. In this way, problems will arise when RTDs of the same standard are used in instrument designs of different standards.